Don't think it's primers or improper cleaning or both sides would be effected. And all my guns are treated the same way after shooting but only the hammer guns have this problem. And only on the left side.

I guess after shooting/cleaning muzzle loaders for 35yrs maybe I got a bit lax in maintaining my breech loaders. For 10 years or so I never oiled the breech face after shooting clays for a day, and never had a problem. And if I would have, I'd never have seen it now. From hence forth I will clean and store them properly. That said, it's still a strange phenomenon.

John;
I agree with you on the WD40 but what do you dislike about the Cheddite primers? I've been using them for about 2 years and have found them comparable to WW209's but cheaper.

In reality, they are probably fine for most uses. But I shoot a lot of old English hammer guns and Cheddites tend to pierce on the firing pin indent way too much. then again, maybe I just have a "bad" brick on my hands. Another lot may be fine.

Then again, they are made in France... (LOL)

I use only Cheddite primers and one of my Parkers on the right side will pierce the primer quite often. On another reloading forum many of the guys have the same complaint when using a couple of high end guns. I believe Cheddite uses a thinner material and if your gun has a primer that reaches out a bit to far they'll pierce. Because I shoot so much, to keep the cost down I use Cheddites. But because I'm rotating between ten different SxS's that one Parker doesn't get shot too much that I believe it's getting hurt a whole lot. One of these days if I get off my lazy a** I'll shorten that one firing pin.

Paul, I can't tell you why on a Molecular level, however I have seen this condition occur frequently on trap over and unders. The bottom barrel is fired much more often than the top barrel. Doubles, the right barrel is fired much more than the left. For whatever reason the least fired barrel tends to be prone to more atmospheric corrosion. I am farily sure it has to do with heat and compression of the steel. Just an observation,

Brad

Brad, thanks for the reply. How's my 1894 Remington C grade coming ?